This invention relates to a method of testing surfactant compositions for urogenital irritancy on individuals having particular susceptibility and to compositions comprising sulfosuccinate monoesters, other anionic surfactants, and betaine surfactants which produce no irritation in the disclosed test. The compositions produce especially fine wet foam, the wetness of which precludes eye sting. It also relates to a method of producing voluminous foam on bath water having the above qualities of freedom from urogenital irritation in susceptible individuals.
Aqueous surfactant compositions have long been used in toiletries for cleaning and foaming. Children in particular enjoy playing with and in foams. Three problems are encountered thereby.
Firstly, exposure of desired duration to desired concentrations of surfactants causes an irritant urethritis and/or vulvovaginitis in susceptible individuals. See for instance S. Marshall, "The Effect of Bubble Bath on the Urinary Tract", J. Urology vol. 93 (1965), p. 112; U. Ravnskov, "Soap Is the Major Cause of Dysuria", Lancet 1984, part 1 , pp. 1027-8; and W. B. Rogers, "Shampoo Urethritis", Amer. J. of Diseases of Children, vol. 139 (1985), pp. 748-9. Huffman et al. , The Gynecology of Childhood and Adolescence (1981 W. B. Saunders) on page 114 observe this "allergic vulvitis" to be distinct from skin irritation: "A soap that does not affect the skin elsewhere on the child's body may, however, cause an allergic vulvitis." Accordingly, it is an object of my invention to provide a surfactant or bubble bath that does not cause such irritation in susceptible persons. It is an object to provide a useful method of testing such products.
Secondly, foams produced by common compositions on bath water soon become dry and brittle. The dryness causes eye sting when the foam contacts the cornea, and the brittleness diminishes the play value and/or the desired pleasant qualities of the foam. I have found a direct relationship between foam dryness and eye sting as hereinafter more clearly disclosed. It is thus a further object of my invent ion to produce a foam that retains its elasticity, softness and wetness.
Thirdly, voluminous persistent foams produced by currently available products leave a skin residue unpleasant to some individuals. My compositions, possibly because they form wetter foams, do not appear to have this drawback, and rinsing is reduced or eliminated.
The prior art acknowledges the desirability of compositions for peri-vaginal cleaning and the foaming of bath water without urogenital irritation. Tom Schoenberg in "Formulating Mild Foaming Bath Products", Cosmetics & Toiletries 100:5, May 1985, pp. 53-7 teaches this object in disclosing several compositions, but uses only skin irritancy as a test criterion. Snoopy Bath Bubbles, a discontinued product of Creative Specialties, Ltd., Jersey City, N.J. 07306, was tested for skin and urogenital irritation on a panel of 24 prepubertal girls (William Waggoner, "Bubble Bath and Bath Products" in Waggoner, ed. , Clinical Safety and Efficacy Testing, Marcel Dekker 1989) Summer's Eve Feminine Wash, a perivaginal cleaner from C. B. Fleet Co. , Lynchburg, Va. 24506, was tested on 150 normal adult women.
It is an object of my invention to provide a testing method using only individuals susceptible to urogenital irritation independently of the presence or absence of skin irritation to other areas of the body. The Snoopy and Summer's Eve tests specifically screened out subjects with a history of susceptibility to urogenital irritation from toiletries. Indeed, my desideratum for both testing and composition is contrary to this prior art teaching which did not fully appreciate the distinction between urogenital irritation (including vulvitis) and skin irritations of other body parts in general.
Eye sting is a subjective symptom reported by subjects when any of various solutions are applied to the cornea. Eye irritation is an objective sign. Ordinarily, a solution which irritates the eye will cause sting in the process. The cornea is also sensitive to increases in osmolarity, and application of a hypertonic solution, even if non-irritating, will ordinarily sting. The strategy extant in the art for countering eye sting, as in baby shampoos, has been to combine a formula low in eye irritancy with polyethoxylates of either monoglycerides or synthetic glycolipids. These nonionic surfactants counter eye sting, but may compromise other qualities of surfactant compositions.
Some prior art compositions teach combining sulfosuccinate monoesters and betaine surfactants as major ingredients, chiefly to reduce skin and eye irritation: Eugene Frank, "Formulation Technology of Liquid Soaps", Cosmetics & Toiletries 97, July 1982, pp. 49-54, Formula 9; Schoenberg, op. cit., and "Formulating Mild Skin Cleansers", Soap/Cosmetics/Chemical Specialties, May 1983, pp. 33-7 and 95; surfactant supply companies Scher, Mona and Jordan, Cosmetics & Toiletries 101 , July 1986, pp. 86-7, formulas for Pearlescent Bubble Bath, Natural Conditioning Bubble Bath, and Mild Bubble Bath; Mona Industries Technical Bulletin #284, January 1985, Mild Baby Bubble Bath. The general idea (but no specific formula range) of such a combination, but with a different object, is also among the many suggested in the disclosure of Morton Pader, U.S. Pat. No. 3,533,955. A sulfosuccinate and betaine are relatively minor constituents of formulas disclosed by Pierre Verunica, U.S. Pat. No. 4,426,310, and may be present in some of the possible formulas in the disclosure of Klisch et al. , U.S. Pat. No. 4,554,098. Such prior art fails to suggest the superiority of such agents and the need to employ them in a major role exclusive of or outweighing other aspects.